A drill chuck of a rotary impact drill can have an axial passage through which the respective percussion action can be transferred from the spindle to an end of the drill which is held between centrically movable and adjustable chuck jaws. The axial stroke or movement can be limited by an abutment which is arranged between the percussion drill spindle and the drill chuck.
A percussion drill apparatus has been described in German Patent Publication DOS No. 3,132,449 which was laid open on July 21, 1983. In this known percussion drill apparatus, the percussion drill spindle has a transverse recess which serves to receive a transverse pin which is fixed in the chuck body. The transverse recess dimension is somewhat greater than the thickness or diameter of the transverse pin, and the connection achieved by the pin prevents rotation of the respective elements which are not to be rotated. Provisions are, nevertheless, made that the spindle has a predetermined free and axial play, which play or clearance is necessary to transmit the percussion action to the drill which is held in the drill chuck.
As long as the percussion drill action is in reaction to a sufficiently large drill reaction or resistance at the drilling location, the path or distance (stroke) of the percussion movement, as well as that of the percussion spindle, is generally smaller than that which is feasible due to the free axial tolerance defined by the transverse connecting pin. In the absence of a resistance, or in the presence of a low resistance to the drill action, the percussion stroke can be larger. In such an event, a considerable portion of the percussion energy is transferred directly from the percussion drill spindle to the drill chuck, whereby the percussion drill spindle impacts with the radial ends of its transverse passages on the transverse connecting pin. The surface areas which are contacted in such action are rather small, and high specific loads per unit area are experienced. This may lead to lasting deformations of the percussion drill spindle and/or the transverse connecting pin. In the long run, this can damage the drill chuck or spindle.